If you are in competition with someone, it usually means you are in a contest for a prize. The prize might just be bragging rights. In nature, the stakes are higher. Organisms must compete for resources necessary for life.

Competition

Recall that
ecology
is the study of how living organisms interact with each other and with their environment. But how do organisms
interact
with each other? Organisms interact with each other through various mechanisms, one of which is competition.
Competition
occurs when organisms strive for limited resources. Competition can be for food, water, light, or space. This interaction can be between organisms of the same species (intraspecific) or between organisms of different species (interspecific).

Intraspecific competition
happens when members of the same species compete for the same resources. For example, two trees may grow close together and compete for light. One may out-compete the other by growing taller to get more available light. As members of the same species are usually genetically different, they have different characteristics, and in this example, one tree grows taller than the other. The organism that is better adapted to that environment is better able to survive. The other organism may not survive. In this example, it is the taller tree that is better adapted to the environment.

Interspecific competition
happens when individuals of different species strive for a limited resource in the same area. Since any two species have different traits, one species will be able to out-compete the other. One species will be better adapted to its environment, and essentially "win" the competition. The other species will have lower reproductive success and lower population growth, resulting in a lower survival rate. For example, cheetahs and lions feed on similar prey. If prey is limited, then lions may catch more prey than cheetahs. This will force the cheetahs to either leave the area or suffer a decrease in population.

Looking at different types of competition, ecologists developed the
competitive exclusion principle
. The principle states that species less suited to compete for resources will either adapt, move from the area, or die out. In order for two species within the same area to coexist, they may adapt by developing different specializations. This is known as
character displacement
. An example of character displacement is when different birds adapt to eating different types of food. They can develop different types of bills, like Darwin’s Finches (
Figure
below
). Therefore, competition for resources within and between species plays an important role in
evolution
through
natural selection
.

An example of character displacement, showing different types of bill for eating different types of foods, in Darwin’s or Galapagos Finches.

Summary

Competition, or when organisms strive for limited resources, can be between organisms of the same species (intraspecific) or organisms of different species (interspecific).

In order for two species within the same area to coexist, they may develop different specializations; this is known as character displacement.